An image that contains only black, white and up to 256 shades of gray.

GIF

Graphic Interchange Format. A file format which can contain up to 256 colours. GIF files are commonly used on the Internet because of their small size and their support by all major browsers. They are a good choice for images containing flat areas of colour and shapes with well-defined edges. Because of the limited colours available in GIF files, it is best to store photographic images in JPEG format. See also: JPEG

GUI

Graphical User Interface. A graphics-based interface used by many operating systems. Its goal is to simplify interaction between the user and the computer. GUIs often use icons and a tracking device such as a mouse.